1. Field of the Invention
The invention pertains to the treatment of a hydrocarbon stream by contacting it with hydrofluoric acid. It is specifically directed to a normal paraffin isomerization process wherein the feed stream is contacted with liquid hydrofluoric acid to thereby remove isomerization catalyst deactivating substances from the feed stream. The invention also relates to an integrated HF alkylation-isomerization process wherein the isomerate produced in the isomerization zone is fractionated in the isostripper and then reacted with a mono-olefin.
2. Description of the Prior Art
As indicated by U.S. Pat. Nos. 3,283,021 (Cl. 260-666) and 3,649,704, the isomerization of normal paraffins is well known in the art. The alkylation of isoparaffins with mono-olefins is also well established as shown by U.S. Pat. Nos. 3,249,650 (Cl. 260-683.48) and 3,729,526.
The problems of isomerization catalyst deactivation caused by impurities in the feed stream is recognized in U.S. Pat. No. 3,506,733 (Cl. 260-683.68), which presents a two-step feed treatment process consisting of passage through a drying agent followed by passage through a bed of molecular sieves. In U.S. Pat. No. 3,760,029, it is disclosed that dimethylsulfide is especially harmful in butane or pentane isomerization. In U.S. Pat. No. 3,729,666 (Cl. 208-278), it is taught that the concentration of nitrogen- and sulfur-containing compounds in a refinery product stream may be reduced by emulsifying the refinery product with spent alkylation acid, mixing spent cracking catalyst with the emulsion and then separating the hydrocarbon and acid phases by settling.
Mercaptans, one form of isomerization catalyst deactivating substance, are sometimes removed by caustic extraction and catalytically promoted oxidation. This is accomplished through the use of catalysts composed of iron group metal chelates in an alkaline environment to promote the oxidation of mercaptans into disulfides which are then decanted. A suitable process is described further in U.S. Pat. Nos. 2,988,500 and 3,260,665 (Cl. 208-206).